The present invention is directed to a hollow drill bit formed by a tubular carrier support part, an annular cutter part and an annular intermediate part extending between the cutter part and the carrier part. The intermediate part and the cutter part are secured together. The intermediate part and the carrier part are soldered together along facing surfaces thereof.
For drilling in hard materials, such as concrete, hollow drill bits with diamond tipped cutting parts are used if it is intended to drill dimensionally accurate holes in a material possibly containing reinforcing steel without causing any noise or jarring.
Conventional hollow drill bits have annular or segment-shaped cutting parts and are connected with a tubular carrier part by sintering for forming a durable and solid connection. When the cutting part, because of wear, reaches the end of its useful life, due to the non-detachable sintered connection the entire drill bit must be scrapped at a high cost.
Therefore, for lowering costs, it is a requirement for such drill bits that the worn cutter parts be detachable from the carrier part so that the worn parts can be replaced by new cutter parts. In this regard, a hollow drill bit is disclosed in CH PS 603 329 having a cutter part connected to a tubular carrier part by an intermediate part or ring. The annular intermediate part is soldered to the carrier part and can be removed along with the cutter part after the soldered connection has been broken and then it can be replaced by another intermediate part with a new cutter part which must be soldered to the carrier part.
Though the connection between the intermediate part and the carrier part is easily detachable because of the soldered connection, the replacement of the intermediate part equipped with a new cutter part requires considerable apparatus and appropriate specialized knowledge to achieve a functional connection and obtain the required true concentric rotation of the drill bit.